The present invention relates to a screw-tightening spindle suitable for use in particular in a bottling plant for tightening caps onto the necks of receptacles.
Screw-tightening spindles are known that comprise a drive socket having an end provided with a threaded collar onto which there is screwed a nut which is secured to a cap-holding chuck which comprises a cylindrical support member fitted with moving jaws. The combination of the threaded collar and the nut provides a removable coupling, thereby enabling the chuck to be replaced for maintenance purposes and more generally making it possible to have a set of interchangeable chucks that match different types of cap. In order to ensure that the jaw-support member is not removed accidentally, the screw pitch of the nut must be irreversible, i.e. the pitch must be short, requiring the nut to perform a plurality of tightening or loosening turns during installation or removal of the chuck. In addition, a plurality of screw-tightening spindles are generally grouped together in a common capping carousel, such that when changing the type of cap in use, chuck replacement requires the bottling plant to be stopped for a length of time that is proportional to the number of screw-tightening spindles mounted on the carousel. Such stoppage reduces productivity.
The invention provides a screw-tightening spindle comprising a drive sleeve associated with a chuck, the chuck comprising a cylindrical support member fitted with moving jaws and being provided on the outside with at least one stud extending radially outwards, the sleeve including at least one slot having a first segment opening out in a free edge of the sleeve and a second segment having an end portion forming an angle relative to the sleeve suitable for retaining the stud in the end portion of the slot when the stud is engaged therein, and the sleeve being fitted with a ring having at least one stop which extends radially inwards from the ring and is received in the slot, the ring being mounted on the sleeve to slide between a locking position in which the stop extends in the first segment of the slot in register with the second segment, and an unlocking position in which the stop is retracted into a third segment of the slot.
Thus, coupling is performed merely by axially displacing the cylindrical support member relative to the sleeve, followed by turning to bring the stud into the end portion of the slot. These two displacements can be performed in a single movement such that mounting the cylindrical support member on the sleeve and removing it therefrom can be performed much more quickly than with a nut while nevertheless ensuring positive locking of the jaw-support member relative to the sleeve.
Advantageously, the second segment of the slot extends from one side of the first segment of the slot such that when the sleeve is rotated, the stud of the cylindrical support member tends to be urged towards the end portion of the second segment of the slot. Thus, the risk of the sleeve and the cylindrical support member being accidentally separated is further reduced.
In a particular embodiment, the first slot segment extends substantially along an axial direction of the sleeve, and the second slot segment extends along a substantially circumferential direction of the sleeve and preferably, the third segment extends in line with the first segment. This makes the slot particularly simple to make.
Also advantageously, the spindle includes means for resiliently urging the ring into the locking position. The coupling is thus locked automatically without any direct manual action being taken on the ring.